[postgis-users] Postgis linear referencing

[Carl Anderson]

On 03/09/2004 05:17:21 PM, Christoph Spoerri wrote:
> Carl,
> 
> I don't know much about the internal of geocoding and never really
> used with
> the exception of mapquest ;), but the system you describe sounds more
> like a
> geocoding system. Something that PostGIS could use as well and (in my
> opinion) seems harder to implement than a LR system.
> 
> Please let me know if I'm wrong here,
> Christoph
>

Christoph,

I have some very specific ideas about LR systems, that may not always  
be in concert with the current industry wisdom.

The common uses of a LR System is to
  generate and show line segments created dynamically from
         the roads network.
  create points representing features along the LR System
  allow the user to retrieve the LR distance from a point along
         the system

so the first element might be a
 (grass cutting | paving | speed limit | street address ) list and
look a little like

Speed Limits
On		    from		    to
Wilson Rd	Jailette Rd		Terry Way		50km/h
Wilson Rd	500m before Porter Ln	500m after Sunset Ct	40km/h
Wilson Rd	6997 Wilson Rd		Johns Pkwy		60km/h
Wilson Rd	Km Post 5.25		Km Post 2.55		90Km/h

so Street name matching is definately a part of the tools
as is relating Intersections to LR offsets (system length)
as is correlating street addresses to a Mile/Km Post measure
as is correlating before and after relationship to system
directions and intersections

We are well on our way to this goal, but co-venturers are welcome
There is a North Carolina DOT System Inventory (of roads) that you,
at Duke Univ, could lay our hands on.  building a suite of tools that  
can process that list, is part of what I would consider LRS support.

BTW you correctly see street addresses as a complex form of a LRS,
not the most complex I can think of BTW.  because people can relate
to Street Addresses in a natural and intuitve way, not including
support for them would leave tools wanting.


C.